Design and implementation of a microscale thermophoresis system based on complementary metal–oxide–semiconductor (CMOS) detector array

Detection of molecular interactions at micromolar to nanomolar concentrations in microliter-scale samples is crucial for drug development and biological research. Microscale Thermophoresis (MST) achieves such measurements by monitoring molecular migration in temperature gradient solutions, with current commercial instruments primarily using single-point sensors based on photodiodes or photomultiplier tubes (PMTs). This study systematically evaluates the performance parameters of PMT vs Complementary Metal-Oxide-Semiconductor (CMOS) imaging technology in MST applications. Results indicate that CMOS imaging technology offers significant advantages in signal-to-noise ratio, dynamic range, and spatial resolution under typical high-photon-flux experimental conditions. In addition, the CMOS-based method enables simultaneous full-field data acquisition, significantly improving measurement efficiency compared to traditional sequential point scanning methods. To this end, we developed an optimized CMOS-based MST platform, integrating automated sample positioning and intelligent region selection methods to ensure measurement consistency. The platform's reliability was verified through standard protein-protein interaction measurements, antigen-antibody binding studies, and small molecule interaction measurements, achieving detection sensitivity comparable to existing technologies. Protein-protein binding curves showed dissociation constants (KD) consistent with surface plasmon resonance method results while successfully measuring protein-small molecule interactions in the micromolar range. This platform provides a technologically advanced solution for biochemical research and drug development applications, particularly for assays involving strong fluorescence signals.